Apparatus for coating paper



Dw 1948- w. BARRETT 2,457, 33

APPARATUS FOR COATING PAPER Filed Nov. 24, 1945 2 Sheets-Sheet 1 INVENTOP VVj "11M Barr-117C ATTORNEY Dec. 28, 1948. w. BARRETT APPARATUS FOR comma PAPER 2 Sheets-Sheet 2 Filed Nov. 24, 1943 n t m M 7. a T NB T w Nu [I Wu 3 Y 5 w Patented Dec. 28, 1948 APPARATUS FOR COATING PAPER William Barrett, International Falls, Minn., assignor to Minnesota and Ontario Paper Company, Minneapolis, Minn.

Application November 24, 1943, Serial No. 511,752

The present invention relates to paper coating and to producing a coating having a. superior surface in respect to flatness, smoothness, suitableness, freedom from imperfections, etc. The raw paper stock in web formmay be of any suitable kind, and the ingredients contained inthe coating applied thereto may be chosen from many different materials.

It is an object of this invention to form a coating upon a fast traveling web of paper. By the term paper as used herein, it is intended to include any and all materials in web form whereon a coating may be applied and treated in accordance with this invention.

This invention has special value Where the finished paper contains a substantial percentage of groundwood stock.

In accordance with this invention the treatment given to a web of paper produces a finished coating either thick or thin, which is uniform, integral, and homogeneous. This may be accomplished at high operating speeds so as to maintain the cost at a minimum. Many of the factors which are responsible for the advantageous results are controllable within certain limits, so it is possible to predetermine to a considerable extent the characteristics of the resulting coating.

Coating has been standard practice for many years and probably since the production of halftone printing, but because of its high costs it has been limited in its general application.

For a better understanding of the present invention, reference will be made to the prior processes of coating. The previous efforts for coating paper may be classified as follows:

(1) Clay or other loading material was added to the paper furnish in the beater or the fan pump. The results were directly proportionate in value to its density, and the amount of the mineral on or near the surface of the paper,

(2) In an effort to eliminate two-sidedness, surface coating material was applied to-the paper at the last wet press.

(3) The next approach was through the application of mineral on the wire. One such application provided for a flow onto the wire with the device operating well down toward the suction box so that the pigment might be fairly well concentrated at the surface.

(4) The next coating expedient consisted of applying coating to the web of paper in varying quantities by means of rolls, brushes or both, and thereafter traveling, smoothing, etc., the coating applied to the paper with various rolls .6 Claims. (CI. 91-55) combinations or brushes to produce a level coated surface on thepaper web. The methods of this type of coating makes possible the application of heavier films but special drying arrangements are needed for setting the coated surface.

(5) The next approach consists of applying the coating in excess quantities to the web by means of brushes, rolls, sprays or the like, the excess coating being removed from the paper web by mechanical doctor or air brushes or doctors.

(6) Another coating process consisted in passing the paper web between two rolls and supplying an excess of coating material at the nip of the rolls; the pressure at the nip between the two rolls being utilized to determine the quantity of coating material applied to the paper.

(7) Still another coating process consists of preparing coating material into a film of substantial weight by preworking by means of a series of rolls and then transferring the film from one of these rolls to the paper web.

In the operation of the present machine a coating of high solid content is spread onto the surface of a roll in a smooth and predetermined thickness which is then transferred to a fast moving web of paper. The coating applied to the paper requires no smoothing or other similar treatment after having been applied,

The apparatus permits the paper to be coated at a speed upward of 1200 feet per minute. Therefore, it is highl desirable that the apparatus for feeding the paper to the coating unit be of such construction that a continuous web of paper is supplied. If the coating unit is em- F ployed ofi a paper machine, a splicing device should be employed so that the paper from a new roll may be spliced to the expiring web while the coating unit is running at a normal coating speed.

The winding apparatus should be so constructed that it will receive a mandrel While the coated paper is being wound upon a second man- 'drel which automatically discharges itself when the intent and desire that the embiment own i herein be deemed illustrative and not restrictive.

and that the patent shall cover all ieatur of patentable novelty existing in the mvention closed, reference being had to the of rather than to the specific description herein to indicate the scope ofthe invention.

'In the drawings forming a of this applicorresponding parts in all the views. In the drawings:

from the ml v, 4 V I gas, etc. In a o the drawing, the drier is shown with gas burners as means for heating. en gas burners dd are employed. it is prefe that ended driers be used.

The coating material may he applied by any suitably constructed coating apparatus but highly successful results have been obed when using a coating apparatus as shown in Figure 2 in which coating material is applied to container lo cation, similar characters of reference indicate 3 Figure 1 is a dlagramatic illustration of the new apparatus.

Figure 2 is aside elevational view of an app ratus for coating only one side of a. moving web.

Figure 3 is a rear view of the felt guiding means.

Figure 4 is a sectional view with parts taken away, showing the drier with a gas heating means positioned therein, and

Figure 5 is a top plan view of the felt guiding T means.

Referring to the drawing in detail it indicates .web of'paper passes over roll l2 and thence be- 1 tween driven tensioning rolls l3. The paper web 1 then passes over roll l5 and over roll it and on its way to the coating unit the web is smoothed upon the surface of the heated drum l9 by means of roll I7; Adjacent to the point where the paper is smoothed on the backing drum, coating unit i8 is positioned. The web is in contact with i the drier drum l9 around the major portion 0 the surface.

After the web has been coated and prior to any substantial formation of drier wrinkles, the

web is contacted by suitable means to hold the wrinkles. at paper take-off roll The coated side of the 1 paper comes in contact with endless felt 28 which coated web in close contact with the drier surface and thence eliminating the formation of drier The dried coated web leaves the drum may be used for preventing the formation of 1 drier wrinkles.

The felt and the paper passes over roll 2! and travel together until they have passed over roll 22. The felt 28 then passes over 1 roll 21, then over automatic felt guide roll and then over spreader roll 26 from which it passes over the jump hitch roll- 24. The position of the roll 24 controls the amount of contact the felt has with the coated paper on the drier roll. In .Figure 2 in dotted lines is shown the position which rolls 24 and 26 may take when the arc of contact of the felt with the coated side of the 1 paper on the drier is increased.

The web of paper then passes around the surface of drier drum 29 after the coating has been applied to said web by coating unit I 8. Associated with the drying means 29 is felt 28a which leaves the surface of the dryingmeans at roll 23a while the paper leaves the surface of the drying means at take-off roll 20a. The felt 28a and the coated paper then travel together over roll 2 la and continue until they pass over roll 22a. The felt then passes over roll 21a and then over spreader roll 26a. The web of paper then passes to the .wind up stand indicated generally at 33.

The web after passing roll 22 on its way to the wind up stand passes over rolls 3!], 3|, and 32.

The drier drum or drums may be heated by any suitable means such as steam, electricity,

di and is'wlthdrawn through conduit d2 by 'clrculatlng pump 43. The coating material is forced through conduit and into a coating fountain 40. A surplus of coating material is maintained at the nip between resilient surfaced applicator roll 31 and the hard surfaced doctor roll 38. The doctor roll has the surface wiped clean by means of a suitable doctor 39.

When-opened ended gas heated drier means are employed it is generally preferred that the gas burners be supported bysultable supports 34 adjacent the surface of a. drier drum surface. As the rotating drier means is adapted to rotate at fairly high speed, it is desirable to secure to the support adjacent the flame, guards 35.

Various means may be employed to prevent the formation of drier wrinkles but one of the most eflective means used so far consists oi a positive driven woven wool endless felt. It is essential that the felt be kept in proper position on the surface of the drier drum and this may be accomplished by means of an adjuster. In Figure 2 the felt passes over felt roll 45 which is supported by bracket 46 which is adjustable and hingedly supported on frame 41 by means of member 48' and nut 48. A bolt 48' extends through member 46' and a removable nut 48 cooperates with the bolt in providing adjusting of the automatic felt guide. Connected to the bracket 46 and extending downwardly is a bracket 49 on which is adjustably secured application roller or felt guide means 50. These guide means 50 fit over the edge of the felt and whenthe felt tends to run to one side the guide 50' through the arm 49 and frame 46 and'roll 46 bring the felt back into the correct position. I

The web to be treated can be coated by the apparatus shown from a fairly slow speed to a speed of from 800 to 1200 feet per minute. A smooth coating is applied to the surface of the applicator roll 31 which transfers the coating to the surface of the paper web. The heated drier drum gives the coating a preliminary set fairly quickly. After the coating has been given this preliminary set, the endless felt which is adjustable as shown in Figure 2 contacts the coated surface of the paper. The felt should come into contact with the coated surface of the web at substantially the time that the drier wrinkles start to form. The position on the drier drum where the drier wrinkles start to appear varies with the type of coatingmaterial, the solid contents of the coating material, the temperature of the drier drum, the weight of the raw stock, and the speed at which the paper is traveling. The point where the felt contacts the coated web may be stated in a different way, i. e., the felt contacts the web as soon as the coating will not be marred by the felt contact.

It is generally preferred that the felt 28 be positively driven at about the speed that the web is traveling. In Figure 2 the roll 23 can be the driving roll for the felt 28.

Roll 23 may be driven by any suitable manner as for example, by a suitable belt SI and roll 52,

roll 52 being driven from any suitable source of power (not shown).

It can be seen that in order to obtain the desired coating the resilient surface applicator roll, the travel of the web over a major portion of the surface of the drier drum, the felt, and the feltguide is highly important.

What I claim is:

1. A device for coating paper which comprises means for passing a web forwardly, a cylindrical backing means carrying the web of paper, a coating unit disposed adjacent the backing means and including a, resilient surfaced roll which contacts the web of paper upon the backing means and positively driven means for holding the coated web in close contact with the backing means surface after the coating material had been given a preliminary set by heat drying during its passage over a portion of the backing surface means, said positively driven means for holding the web in close contact with backing means being located a considerable distance around the periphery of the backing means in the direction of movement of the web from the position of the coating unit.

2. A device for coating paper which comprises, means for passing a Web of paper forwardly, a coating unit including a resilient surfaced applicator roll for applying a film of coating material to said moving web of paper, cylindrical drying means for drying the coating material applied to the paper, and a moving felt mounted adjacent the drying means for holding the coated paper in close contact with the surface of the drying means after the coating has received a preliminary set by heat drying during the passage of the coated paper over a portion of the drying means said moving felt being located a considerable distance around the periphery of the drying means in the direction of movement of the web from the position of the coating unit.

3. A device for coating paper which comprises, means for passing a web of paper forwardly, a coating unit including a resilient surfaced applicator roll which contacts the web of paper for transferring the film of coating material to the paper, means for supplying coating material to the applying roll, means for smoothing the coating on the applying roll prior to the application of the coating material to the paper, a heated drying roll for drying the coated material applied to the paper, and means for holding the paper in close contact with the surface of the drying roll after the coating material has been given a preliminary set during the passage of the paper over a portion of the drying surface prior to any contact with the coated surface said means for holdin the paper in close contact with the surface of the drying roll being located a considerable distance around the periphery of the drying roll in the direction of movement of the web of paper from the position of the coating unit.

4. A device for coating 9. moving web of paper which comprises, a coating unit which includes a roll for applying a smooth film of coating material to the paper and a roll for smoothing the coating onthe applying roll, cylindrical heated drying means for drying the coating material applied to the paper. and a moving felt for holding the coated web of paper in close contact with the surface of the drying means after the coating has received a preliminary set by heat drying during the passage of the paper over a portion of the drying means said moving felt being located a considerable distance around the periphery of the drying means in the direction of movement of the web from the position of the coating unit.

5. A device for coating paper comprising, a coating unit which includes means for applying a film of coating material to a moving web of paper, cylindrical drying means for drying the coating material applied to the paper, and a moving felt mounted adjacent the drying means for holding the coated paper in close contact with the surface of the drying means after the paper has received a preliminary set by heat drying during the passage of the coated paper over a portion of the drying means said moving felt being located a considerable distance around the periphery of the drying means in the direction of movement of the web from the position of the coating unit.

6. A device for coating paper which comprises means for passing a web of paper forwardly, a heated dryer drum, means for carrying the web around the major portion of the surface of the dryer drum, a coating unit disposed adjacent the dryer drum and comprising a roll which contacts said web upon said drum, and means for depositing a coating material on the said roll, a second roll for smoothing the coating material upon the first roll, and means for holding the coated web in close contact with the drying drum surface after the coating material has been given a. preliminary set during passage of the web over a portion of the dryer drum, said means for holding the coated web in close contact with the dryer drum being located a considerable distance around the periphery of the drying drum in the direction of the movement of the web from the position of the coating unit.

WILLIAM BARRETT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

